Added opportunistic send functionality to cmd_msg

If policy is set to 'opportunistic' then when the user executes cmd_msg it will append the otr whitespace tag to the message

The other client should start AKE once it receives the message.

TODO: Analyze incoming messages for whitespace tag

src/otr/otr.h

@@ -23,6 +23,8 @@
 #ifndef OTR_H
 #define OTR_H
 
+#define OTRL_TAG " \t  \t\t\t\t \t \t \t  "
+
 #include "config/accounts.h"
 
 void otr_init_module(void);

src/otr/otrlibv4.c

@@ -108,6 +108,8 @@ otrlib_encrypt_message(OtrlUserState user_state, OtrlMessageAppOps *ops, char *j
 {
     gcry_error_t err;
 
+    ops.policy = OTRL_POLICY_SEND_WHITESPACE_TAG;
+
     err = otrl_message_sending(
         user_state,
         ops,